The present invention relates generally to a proximity probe and, in particular, to an encapsulated proximity probe and its manufacturing method for providing an accurate encapsulated proximity probe that is impervious to the predations of its environment and that is used to, inter alia, monitor vibration of rotating and reciprocating machinery.
Proximity probe systems that analyze and monitor, for example, rotating and reciprocating machinery are known in the art. These systems typically include one or more proximity probes: noncontacting devices that measure displacement motion and position of the observed conductive target material relative to the probe. Typically, each proximity probe is located proximate a target object such as a rotating shaft of a machine or an outer race of a rolling element bearing being monitored and is connected to conditioning circuitry which in turn is coupled to analyzing apparatus for data reduction and display. By known techniques, these systems analyze and monitor rotating and reciprocating machinery for providing, inter alia, indications of incipient problems. A variety of proximity probe systems with a variety of different proximity probes are at the present time being sold by the assignee of this application, Bently Nevada Corporation of Minden, Nev.
In general, proximity probes are required to operate with precision under very adverse physical, chemical, and mechanical conditions and are often difficult to replace. Thus, there is an ongoing effort to make the proximity probe one of the most accurate and reliable parts of any proximity probe system.
The assignee""s untiring commitment to improving proximity probes and the methods of manufacturing such probes for making the proximity probe one of the most accurate and reliable parts of any proximity probe system is chronicled in the seven patents to Van Den Berg (U.S. Pat. Nos.: 6,131,270; 6,131,267; 6,072,312; 5,818,224; 5,770,941; 5,712,562; and 5,685,884), the two patents to Schutts (U.S. Pat. Nos.: 5,021,737 and 5,016,343), and the single patent to Van Den Berg, et al. (U.S. Pat. No.: 5,351,388) all of which are hereby incorporated by reference in their entireties. However, it is stipulated that none of these references teach singly nor render obvious when considered in any conceivable combination the nexus of the present invention as disclosed in greater detail hereinafter and as particularly claimed.
Hence, the assignee""s patents as identified hereinabove reflect a line of proximity probes and the methods of manufacturing such probes. In their essence, these patents delineate a variety of different proximity probe tips, a variety of different bobbin or preform configurations, and how proximity probe manufacturing has evolved from the process of simply placing and epoxying a plastic insulating cap over a combined sensing coil, bobbin (or preform) and a fixed cable length assembly to an injection molding process of the coil, bobbin (or preform) and the fixed cable length assembly using radial and axial pin pulling techniques.
Heretofore, both the epoxying process and the injection molding process used to cover the sensing coil have been known to leave seams or interruptions that are susceptible to, inter alia, predations of the environment such as fluid and/or vapor ingress (e.g., oil, oil vapor, water, and/or water vapor) into the interior of the probe thereby causing probe deterioration leading to, inter alia, inaccurate and unreliable probe measurements.
For example, the pins employed in the radial and axial pin pulling process have been known to cause areas that fail to be filled in with moldable material during the encapsulation process such that an opening, slit, or the like is formed that allows fluid and/or vapor ingress into the interior of the probe thereby causing probe deterioration leading to, inter alia, inaccurate and unreliable probe measurements.
Furthermore, the radial and axial pin pulling processes are problematic in that the sensing coil, preform and fixed cable length assembly may become misaligned within the encapsulation thereby altering the desired spacing between a target object and the sensing coil of the probe such that inaccurate and unreliable measurements are obtained when in operation.
Specifically, it is critical that the displacement motion or position between the target object and the sensing coil of the proximity probe remains within the linear range of the proximity probe for providing accurate and reliable measurements over a wide range of circuit and environmental conditions in order to operate rotating and reciprocating machinery safely and efficiently. Thus, if the coil becomes skewed within the encapsulation the displacement motion or position between the target object and one area of the skewed coil will be different than the displacement motion or position between the target object and another area of the skewed coil thereby providing erroneous and undependable probe measurements when in operation. In fact, if the coil becomes skewed within the encapsulation the displacement motion or position between the target object and the sensing coil may completely fall out of the linear range of the proximity probe resulting in flawed probe measurements when in operation.
Moreover, a typical pin pulling process requires locating and aligning each of the coil and cable assemblies within a lower mold cavity via radial and axial pins, lowering or closing an upper mold cavity, injecting moldable material within the mold cavities, retracting the pins and further injecting moldable material within the mold cavities heretofore occupied by the retractable pins for fully encapsulating the coil and fixed cable length assembly. Hence, the pin pulling process requires that the molds be outfitted with precision retractable pins that are required to keep the coil and fixed cable length assembly located and aligned within the mold cavity during a first injection process. Then, the pins are timely retracted with precision such that the coil and cable assembly remains properly located and aligned within the mold cavity during a second injection molding process that fills the areas previously occupied by the retractable pins. Thus, this process not only requires a precision mold but also requires retractable pins to be movably disposed within the mold with precision. Additionally, this process requires pin actuators for moving the pins into and out of the mold cavity and supporting electronics that may require programming for orchestrating the timing of pin insertion and retraction. As a result, the pin pulling process relies on a multiplicity of components operating with precision and in synchrony for carrying out the two-step encapsulation process delineated in the prior art noted hereinabove.
For the foregoing reasons, there is a need for a proximity probe that is impervious to the predations of the environment and a method of manufacturing such a probe whereby the manufacturing problems and complexities of the prior art manufacturing processes are substantially eliminated.
Specifically, there is a need for a method of manufacturing proximity probes that can be repeatedly used to encapsulate sensing coils in a symmetrically manner (i.e., without the coils being skewed within the encapsulation). Additionally, there is a need for a method of manufacturing proximity probes that eliminates interruptions, openings, slits or the like that are formed within the encapsulation by internal parts such as sleeves covering the sensing element and/or by the encapsulation (injection molding) process itself. Furthermore, there is a need for a method of manufacturing proximity probes that eliminates the retractable pins, the pin actuators, and the supporting electronics associated with the prior art processes thereby eliminating the expense, unreliability and time consumption associated with these processes.
The present invention is distinguishable over the known prior art in a multiplicity of ways. For one thing, the present invention provides a method of manufacturing a proximity probe that can be repeatedly used to encapsulate a sensing coil in a symmetrical manner (i.e., without the coil being skewed within the encapsulation) and that eliminates interruptions, openings, slits or the like that are formed within the encapsulation by internal parts such as a sleeve covering the sensing coil and/or by the encapsulation (injection molding) process itself. Additionally, the present invention provides a method of manufacturing a proximity probe that eliminates the prior art pin pulling and two step encapsulation processes thereby eliminating the expense, unreliability and time consumption associated with these processes. Particularly, and in stark contrast to the known prior art, the present invention provides a single step encapsulation process and means for retaining the radial and axial orientation of the sensing coil within the mold cavity while eliminating the manufacturing problems and complexities of the known prior art processes thereby providing a simple, quick, and unfailingly repeatable method of manufacturing a proximity probe.
In its simplest form, and in accordance with the present invention, the proximity probe manufacturing method comprises the steps of: providing a preform supporting a coil at a forward end and including an open ended interior cavity at a rearward end; inserting a support pin into the interior cavity such that an end of the support pin emanates from the rearward end of the preform; using the end of the support pin emanating from the rearward end of the preform for supporting the coil and preform on the support pin and within a mold cavity, and injecting moldable material into the mold cavity during a single injecting step for molding an encapsulation of material ensconcing the coil and preform thereby generally defining an encapsulated probe tip of a proximity probe that is subsequently formed by coupling a cable to the encapsulated probe tip.
More particularly, and in accordance with one preferred form of the present invention, the proximity probe manufacturing method includes providing a preform having an interior cavity accessible by an opened rearward end. A coil is coupled to the preform proximate a forward most end of the preform for defining a coil and preform assembly. A support pin is then axially located through the opened rearward end of the preform and into its interior cavity such that an end of the support pin emanates from the opened rearward end of the preform. The end of the support pin is then cantilevered between an upper and a lower mold plate for supporting the coil and preform assembly on the support pin and within a mold cavity defined by the upper and lower mold plates. Next, moldable material is injected into the mold cavity for molding an encapsulation of material over the coil and preform assembly wherein the encapsulated coil and preform assembly generally defines an encapsulated probe tip which when coupled to a cable generally defines a proximity probe. Hence, one hallmark of the present invention is supporting, within a mold cavity, the coil and preform assembly from the interior of the preform thereby eliminating any obstructions from interfering with the encapsulation of the coil and preform assembly formed by the injection molding process for providing a superior encapsulated proximity probe.
Also in accordance with the present invention, and in one preferred form, the proximity probe is comprised of a preform comprised of an elongated body having a forward most end and a rearward most end. The forward most end of the preform includes a hollow annular recess integrally formed with the preform and transitioning into a centering bore extending into the elongated body of the preform for receiving a mounting pin on which the sensing coil is mounted such that the receipt of the mounting pin with the centering bore centers the coil along a longitudinal axis of the preform and such that the sensing coil is received in the annular recess and affixed thereto by an adhesive interposed between the sensing coil and the annular recess thereby defining a coil and preform assembly. This coil and preform assembly configuration allows tuning of the coil by removing turns of wire from its center. The proximity probe further includes an encapsulation of moldable material ensconcing the coil and preform assembly wherein the encapsulated coil and preform assembly generally defines an encapsulated probe tip connectable to any cable length for generally defining a proximity probe.
Furthermore, through bores may be integrally molded within the encapsulation during the injection molding process and can be employed in coupling a cable of any length to the encapsulated probe tip. In one particular form, the through bores are molded in open communication with a rearward interior cavity of the preform, the cavity having an opened end. A stripped end of a cable is inserted into the rearward interior cavity via the opened end such that an exposed portion of a braided conductor at the stripped end of the cable is in open communication with the through bores. Solder is then inserted into the through bores, melted, and allowed to flow along the braided conductor and into contact with an interior of a ferrule molded in the preform and circumscribing the braided conductor for providing an electrical and mechanical coupling of the cable to the encapsulated probe tip.
Moreover, and in accordance with one preferred form of the present invention, a proximity probe metal casing and interlocking method is provided wherein the metal casing is comprised of an elongated cylindrical structure having a sidewall defining a bore transitioning from a leading end to a trailing end of the structure, the sidewall including at least one geometrically shaped opening disposed through the sidewall and terminating in the bore. The interlocking method is comprised of sliding the metal casing over the cable and onto the encapsulated probe tip and then linearly positioning the metal casing to any discrete location on the encapsulated probe tip. Next, the interlocking method includes applying heat to the metal casing for melting a portion of the underlying encapsulation and allowing the melted portion of the encapsulation to dispense into the geometrical opening disposed within the metal casing thereby interlocking the metal casing to the encapsulation at the linearly positioned location and providing a means for providing case trim adjustment.
Accordingly, a primary object of the present invention is to provide a new, novel and useful proximity probe and a proximity probe manufacturing method.
A further object of the present invention is to provide a proximity probe as characterized above which includes an encapsulated proximity probe tip manufactured by an injection molding process encapsulating a sensing coil and preform assembly in moldable material and in the absence of a cable connection.
Another further object of the present invention is to provide an encapsulated proximity probe tip as characterized above that is coupled to any length of cable after the injection molding process of encapsulating the sensing coil and preform assembly in moldable material.
Another further object of the present invention is to provide the proximity probe manufacturing method which includes eliminating both axially retractable and radially retractable support pins that respectively provide localized support at the front and sides of a coil and preform assembly and replacing all of these retractable support pins with a single support pin received within an opened interior of the preform along a longitudinal axis and via an opened rearward end distal from the sensing coil disposed at a forward most end of the preform.
Another further object of the present invention is to provide the proximity probe manufacturing method as characterized above which includes cantilevering between an upper and a lower mold plate an end of the support pin emanating from the opened rearward end of the preform for interiorly supporting the coil and preform assembly within a mold cavity defined by the upper and lower mold plates such that the coil and preform assembly is supported from within the preform by the support pin coacting with the opened interior of the preform.
Another further object of the present invention is to provide the proximity probe manufacturing method which includes molding an encapsulation of material over the coil and preform assembly for forming the encapsulated proximity probe tip and forming in such molding step a through bore passing through a sidewall of the encapsulation and terminating in open communication with the opened interior of the preform such that solder can be passed through the sidewall of the encapsulation to a braided conductor of a cable that has been previously inserted into the opened interior of the preform via an opened back end of the encapsulation and the opened rearward end of the preform wherein when the solder is melted it flows along the braided conductor and into contact with an interior of a ferrule disposed within the opened interior of the preform for electrically and mechanically connecting the braided conductor to the encapsulated proximity probe tip.
Another further object of the present invention is to provide the proximity probe manufacturing method which includes molding at the forward most end of the preform a annular recess having a hollow interior circumscribing and defining an opening of a blind bore internally disposed within the preform along its longitudinal axis.
Yet another further object of the present invention is to provide the proximity probe manufacturing method which includes affixing the sensing coil having a hollow interior to the annular recess by mounting the sensing element via its hollow interior on a mounting pin, passing the mounting pin through the hollow interior of the annular recess and into the blind bore of the preform such that the coil is centered along the longitudinal axis of the preform and such that a back face of the coil having adhesive disposed thereon abuts an annular ledge of the annular recess.
Still yet another further object of the present invention is to provide a proximity probe and a proximity probe manufacturing method which eliminates costly machining of internal threads into a metal case which typically circumscribes the encapsulation of the encapsulated proximity probe tip by providing a metal casing having a geometrical opening within the metal casing, placing the metal casing on the encapsulated proximity probe tip, linearly positioning the metal casing on the encapsulated proximity probe tip at a location relative to the coil and heating the encapsulation proximate the geometrical opening such that a melted portion of the encapsulation is displaced into the geometrical opening for interlocking the metal casing to the encapsulation at the linearly positioned location.
These and other objects and advantages will be made manifest when considering the following detailed specification when taken in conjunction with the appended drawing figures.